The present invention relates to a system for collectively administering a plurality of copiers, printers or similar image forming apparatuses connected to a control station by a communication line.
A trouble estimating device is conventional which estimates a trouble to occur in an image forming apparatus by monitoring signals output from the apparatus. For example, Japanese Patent Laid-Open Publication No. 58-221409 teaches a device of the type measuring time intervals at which sensors monitoring the operating conditions of the apparatus output signals, producing statistics, including mean values, deviations and variations, on the basis of the intervals, storing them in a memory, comparing the stored statistics with corresponding limit values stored in the memory beforehand, and displaying an estimated trouble when any one of the statistics exceeds the associated limit value.
In practice, however, an image forming apparatus generates a number of signals during the course of image formation. Hence, the conventional trouble estimating device described above needs a memory having a capacity great enough to accommodate all the statistics derived from the different kinds of time intervals and all the limit values corresponding thereto. Moreover, the procedure for producing the statistics is complicated. When the device is mounted on an image forming apparatus, it produces the individual statistics for every image forming cycle of the apparatus. This complicates the control over the apparatus and is apt to adversely effect the image forming operation.